The inventors of the present invention devised a method and apparatus for regulating the transport of a preselected ion across a cell membrane utilizing an applied, oscillating magnetic field. This remarkable achievement is disclosed in U.S. patent application Ser. No. 923,760, now U.S. Pat. No. 4,818,697 entitled, "Techniques for Enhancing the Permeability of Ions", which was filed on Oct. 27, 1986, and the disclosure of which is incorporated herein by reference. Therein, a method and apparatus are disclosed by which transmembrane movement of a preselected ion is magnetically regulated using a time-varying magnetic field tuned to the cyclotron resonance energy absorption frequency of the preselected ion. This important discovery brought to light the interplay of local magnetic fields and the frequency dependence of ion transport mechanisms.
Having established a method by which selective ion transport can be regulated, the present inventors discovered that certain characteristics of living tissue could be controlled by application of an oscillating magnetic field having a non-zero average value. Significantly, it was determined that selected ratios of the frequency of the applied field to the flux density of the total magnetic field passing through the tissue along a predetermined axis were capable of stimulating the growth and development of the target tissue. This was demonstrated to be effective in promoting the growth of bone tissue. As a result, U.S. patent application Ser. No. 172,268, entitled "Method and Apparatus for Controlling Tissue Growth with an Applied Fluctuating Magnetic Field" was filed on Mar. 23, 1988, the disclosure of which is incorporated herein by reference.
Therein, there is provided an apparatus for controlling the growth of living tissue. The apparatus includes magnetic field generating means such as a field coil for generating a controlled, fluctuating magnetic field which penetrates a tissue, and an associated magnetic field sensing device for measuring the intensity of the magnetic field present in the tissue. In one embodiment, the magnetic field generating means and magnetic field sensor are enclosed within a housing along with a power source.
The work with tissue growth control was extended and it was discovered that tissue development can be regulated to control the growth characteristics of non-osseous, non-cartilaginous connective tissue proper and cartilaginous tissue. These inventions are disclosed, respectively, in U.S. patent application Ser. No. 254,438, entitled "Method and Apparatus for Controlling the Growth of Non-Osseous, Non-Cartilaginous Solid Connective Tissue", which was filed Oct. 6, 1988, the disclosure of which is incorporated by reference, and in U.S. patent application Ser. No. 265,265, entitled "Method and Apparatus for Controlling the Growth of Cartilage", which was filed Oct. 31, 1988, the disclosure of which is incorporated by reference.
This work further resulted in an apparatus which utilizes a feedback system to provide automatic control of the magnetic field in any application of cyclotron resonance transmembrane ion regulation. This invention is disclosed in U.S. patent application Ser. No. 278,688, filed Dec. 1, 1988, entitled "Improved Method and Apparatus for Regulating Transmembrane Ion Movement" by the inventors of this application, now U.S. Pat. No. 5,059,298. This disclosure has been incorporated by reference.
In U.S. Pat. No. 4,616,629, to Moore, a single-coil configuration adapted for embedment in an orthopedic cast for use in applying electromagnetic signals for osteogenic therapy is provided. Therein, an otherwise flat circular multiple turn coil is permanently deformed and is preferably embedded within a cast. The disclosure does not include the use of a Helmholtz configuration of a coil pair to create a uniform magnetic field within a predetermined space. The Moore disclosure does not recognize any need to determine the local magnetic field component nor is any means for measuring and automatically compensating for fluctuations in the local field provided.
It will be recognized by those skilled in the art that an idealized magnetic field occupying the space between two coils in Helmholtz configuration can be easily predicted where the coils are flat and circular. However, as the coils deviate from this geometry calculation of an applied field becomes more difficult.
It will also be appreciated that the application of a therapeutic magnetic field to a region of body tissue of either man or animal generally requires that the patient remain ambulatory to the extent possible. Thus, it is highly desirable to have an apparatus such as that disclosed by the present inventors in prior applications which can be attached to a patient and which does not substantially restrict patient movement. It would also be desirable to provide such an apparatus in which the coils that make up the Helmholtz coil pair could be adapted to conform to differences in the shape of the site of application i.e. leg, arm, or the like, and which could be reused on a number of patients having different morphological characteristics. The present invention meets these goals.
In accordance with the present invention, there is provided a deformable tissue growth stimulator which includes a pair of field coils which can be deformed to fit a range of sizes and shapes of patients and body regions. In one aspect, each coil is encased or embedded in a plastically deformable medium to form twin deformable coil pads. The pads are interconnected by a flexible belt which is provided with means for attaching the belt around a region of living tissue to be treated such as a patient's leg. In use, the treatment pads are simply bent with one's hand or the like to match the contour of the patient's body, such as a patient's arm or leg. The nature of the material in which the coils are embedded allows this plastic deformation without any resilient recoil. Once the treatment pads have been deformed in this manner, the belt is secured in position on the subject limb and treatment is administered. As will be explained more fully, the precise ratio of frequency to average magnitude of a composite magnetic field which permeates the target tissue is maintained in a manner which automatically corrects for deviations in the local magnetic field to which the tissue is subjected.